#gil global interpreter lock （cpython）
#python中一个线程对应于c语言中的一个线程
#gil使得同一个时刻只有一个线程在一个cpu上执行字节码, 无法将多个线程映射到多个cpu上执行

#gil会根据执行的字节码行数以及时间片释放gil，gil在遇到io的操作时候主动释放
# import dis
# def add(a):
#     a = a+1
#     return a

# print(dis.dis(add))

# total = 0

# def add():
#     #1. dosomething1
#     #2. io操作
#     # 1. dosomething3
#     global total
#     for i in range(1000000):
#         total += 1
# def desc():
#     global total
#     for i in range(1000000):
#         total -= 1

# import threading
# thread1 = threading.Thread(target=add)
# thread2 = threading.Thread(target=desc)
# thread1.start()
# thread2.start()

# thread1.join()
# thread2.join()
# print(total)

total = 0
def add():
    global total
    for i in range(100000):
        total += 1
def desc():
    global total
    for i in range(100000):
        total -= 1
import threading
thread1 = threading.Thread(target=add)
thread2 = threading.Thread(target=desc)
thread1.start()
thread2.start()
thread1.join()
thread2.join()
print(total)
